1. Field of the Invention
Exemplary embodiments of the present invention relate to a three dimensional shape measurement apparatus. More particularly, exemplary embodiments of the present invention relate to a three dimensional shape measurement apparatus measuring a three dimensional shape by illuminating a grating pattern light.
2. Discussion of the Background
Generally, a three dimensional shape measurement apparatus illuminates a grating pattern light onto a measurement target and photographs a reflection image by the grating pattern light to measure a three dimensional shape of the measurement target. The three dimensional shape measurement apparatus typically includes a stage, a camera, an illumination unit, a central processing section, etc.
Typically, measuring a three dimensional shape of a measurement target by using the three dimensional shape measurement apparatus is performed as follows.
First, a grating pattern light from the illumination unit is incident onto a measurement target disposed on the stage. The grating pattern light is incident onto the measurement target while moving N times. Thereafter, the camera acquires N pattern images of the measurement target by detecting the grating pattern light reflected by the measurement target. Then, the central processing section calculates height for each location from N pattern images by using an N-bucket algorithm. The three dimensional shape of the measurement target is measured by using the calculated height for each location.
A conventional three dimensional shape measurement apparatus illuminates grating pattern lights in a plurality of directions to precisely measure a three dimensional shape. The three dimensional shape can be measured only when transferring a grating pattern for generating the grating pattern light by N times in a direction parallel with illumination direction of the grating pattern light when viewed in a plan view. Thus, a conventional transfer direction of the grating pattern is substantially in parallel with an arrangement direction of the grating pattern, i.e., substantially perpendicular to an extension direction of the grating pattern. Accordingly, when viewed in a front view, a grating unit disposed at a left side has been transferred from lower left to upper right, and a grating unit disposed at a right side has been transferred from lower right to upper left.
Since it is difficult that transferring two grating units by using one grating transfer unit is directly performed, conventionally, independent grating transfer units has been employed corresponding to a plurality of directions, or the transfer direction has been obtained by using a predetermined optical system such as a reflection minor.
However, when the independent grating transfer units and the optical system are employed for grating pattern light, manufacturing cost is increased for installing the plurality of grating transfer units or the optical system, and it is required to independently control and manage the grating transfer units or managing the optical system.